To improve the light emitting efficiency of a light emitting device including a nitride semiconductor, a quantum well structure in which an InGaN well layer is sandwiched between barrier layers with a band gap energy larger than that of the well layer is used.
For such a light emitting device, crystal needs to be grown at a lowest possible temperature for facilitating the incorporation of In in the formation of the well layer. However, as the temperature for the crystal growth becomes lower, the crystalline quality becomes more deteriorated. Accordingly, to enhance the efficiency of the semiconductor light emitting device, it is important to form a high-quality crystal while ensuring the incorporation of In.
In JP-A 2004-297098 (Kokai), a nitride semiconductor light emitting device is described in which intermediate layers made of AldGa1−dN (0.30≦d≦1) are formed between well layers and barrier layers of an active layer in a quantum well structure. The intermediate layers are formed respectively on all the well layers and has a band gap energy larger than that of the barrier layer. However, even this technology is used; there is room for improvement in terms of enhancing the light emitting efficiency.